[asterisk-users] Duplicate DTMF

[C. Chad Wallace]

At 10:22 PM on 09 Sep 2009, John A. Sullivan III wrote:

> Hello, all.  I've come across a nasty problem just as we are ready to
> put our first system into production.  During our final testing, we
> were plagued with several "invalid extension" or "password incorrect"
> messages when we knew the information entered was correct.  Upon
> investigation, we saw that DTMF signals were occasionally but not
> consistently duplicated.  We might dial extension 1234, see 1234 on
> the phone from which we dialed, but see 112334 on the Asterisk
> console.
> 
> We have seen this from cell phones calling via the PSTN (we use a SIP
> trunking carrier and do not handle the PSTN interface ourselves);
> we've seen it from land line phones via the PSTN, and have even seen
> it internally from our own Snom SIP phones.
> 
> dtmfmode=auto but we have also tried setting it to rfc2833 and we have
> tried relaxdtmf set to both yes and no.
> 
> We are running Asterisk 1.6.1.6 on CentOS 5.3.  We really don't know
> what more to do to fix it.  Googling shows that others have had this
> problem but I haven't seen a clear resolution other than playing with
> relaxdtmf.  How do we solve this problem? Thanks - John

When we had that problem, it turned out it was caused by the txgain
being too high (10.0).  I dropped it down to 5.0, and the DTMF problems
went away.

Have you tuned your gains using a milliwatt line and ztmonitor?

I followed this howto:  http://www.mattgwatson.ca/?p=14

But that led to the ridiculous txgain setting of 10.0 on all my ports,
which I later clawed back to 5.0 to fix the DTMF issue.  Maybe I did it
wrong?  Anyway, the rxgain settings I got from that procedure seemed to
improve our call quality.  We've since moved to a partial PRI instead
of those analog lines, so we don't have to worry about that anymore. :-)

-- 

C. Chad Wallace, B.Sc.
The Lodging Company
http://www.skihills.com/
OpenPGP Public Key ID: 0x262208A0

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